Endophytic fungel infection of grasses has been recognized for nearly one hundred years. An "endophyte" is defined as "an organism that lives its life cycle within a host plant without causing disease". Fungal endophytes exist exclusively in the intercellular spaces of the plants, primarily in sink tissues of the plant, such as leaf sheaths and pith. The endophytes do not invade the plant cells and their presence is often completely asymptomatic.
Fungal endophytes infect many wild and cultivated grass species and these associations have major ecological and agricultural impacts. Many of the endophytic fungi which infect commercially important forage and turfgrasses belong to the genus Epichloe and its asexual anamorphs which have been classified as Acrernonium section Albo-lanosa. Clay, Ecology, 69, No. 1, 10-16 (1988). In the case of the asexual Acrernonium spp., infection of the host causes no symptoms. One grass which is endophytically infected by Acrernonium typhinum is the highly apomictic big blue grass (P. ampla) cultivar Service (PI387931), released by the Alaska Department of Natural Resources as an improved grass for roadside vegetation.
In many instances, the endophyte-grass association is strictly symbiotic, with the fungus conferring benefits on the plant. One of these benefits is reduced herbivory by insects and animals due to the production of toxic alkaloids. A major drawback of endophyte infection however is that toxic alkaloids in endophyte-infected forage grasses can cause grazing livestock to be poisoned.
The insect deterrence conferred by Acremonium endophyte infection imparts considerable advantage to forage and turfgrass. Therefore, turfgrass breeders wish to improve grasses through use of new combinations of endophytes and grasses. It is known, however, that there is limited compatibility between various endophyte isolates and grasses other than their natural hosts; most attempts to produce novel endophyte-host relationships have failed. This seems to be due to the fact that the specific interactions between the fungal endophytes and their host grasses which result in effective infection are completely unknown.